the histological effects of two chitin synthesis inhibitors (CISs) on the larvae of the cotton leafworm were investigated under the laboratory conditions. Restts obtained grown 4th instar larvae showed that tredtment of the 4th with CISs revealed many ultrastructural alterations in the midgut of the 6th instar larva. These alterations appeared clearly in the cytoplasm, the nuclei and cell organelles. The histology and ultrastructure of the alimentary canal, and the mid gut in particular have revealed various effects of tow tested CSIs. Obtained results indicated that CSIs could be good substitutes for traditional chemical insecticides for controlling S. littoralis due to their effect on midgut epithelial cells which may lead to malnutrition and eventually death.